DCI: - DCI (Downlink Control Information) is transmitted from the eNodeB (also known as eNB, which is the base station in LTE networks) to the UE (User Equipment)
eNodeB
to UE:
·
The eNodeB transmits DCI to the UE in the downlink direction. DCI carries critical information regarding the
scheduling of downlink and uplink resources. This includes information like
resource block allocation, modulation and coding scheme, HARQ (Hybrid Automatic
Repeat Request) process, and power control commands.
·
The DCI is embedded in the PDCCH (Physical Downlink
Control Channel), which is responsible for informing the UE about where to find
its allocated data in the LTE frame structure.
·
After receiving the DCI, the UE knows which time-frequency resources it
should use for either receiving downlink data or sending uplink data.
·
DCI formats are required to tell the UE how to get its data which is
transmitted on PDSCH in the same Subframe.
·
PDCCH is a control channel that carries DCI information. DCI is like a
map for a UE to find and decode PDSCH from the resource grid.
The DCI
format gives the UE, details such as:
·
Number of resource blocks
·
Resource allocation type
·
Modulation scheme
·
Transport block
·
Redundancy version (RV)
·
Coding rate
·
CQI
·
CSG info
Here is an
example of how DCI formats are used:
·
The eNB wants to send data to a UE.
·
The eNB selects a set of resource blocks
on the PDSCH to carry the data.
·
The eNB encodes the data into a transport block.
·
The eNB encodes the DCI information for the transport block.
·
The eNB transmits the DCI information on the PDCCH.
·
The UE receives the DCI information and decodes it.(DCI = 0 For SSS additions)
·
The UE uses the DCI information to decode the transport block on the PDSCH.
· Once the UE has decoded the transport block, it can extract the data that was intended for it.
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